9 8 Book of Steamships 



After the model, came a launch tried on 

 the Thames. As first made, the propeller 

 resembled a screw far more than it does 

 to-day. There were several blades. Whilst 

 the Francis Smith was on one of her trials, 

 half the screw was accidentally broken off. 

 Though the people aboard did not know 

 what had happened at the time, they had 

 noticed a sudden acceleration in the speed 

 of the launch. Subsequent examination 

 and experiment determined the fact that 

 one could have too many blades on a 

 propeller or too much blade area. I should, 

 perhaps explain that the first propeller 

 was of wood, hence the breaking. Subse- 

 quently metal was used, and to-day 

 manganese-bronze is about the best 

 material that can be used for this 

 important component of the steamship. 



We soon find several vessels of rather 

 small tonnage being fitted with the screw, 

 and the Admiralty's attention was called 

 to this method of avoiding the objection- 

 able paddle-wheels for warships. Again 



